Dialkyl sulfosuccinates are a class of surfactants used as emulsifiers, dispersants, wetting agents, and adjuvants. An example of a dialkyl sulfosuccinate is sodium dioctyl sulfosuccinate (DOSS). DOSS is a waxy, sticky, granular solid, which is difficult to handle. It tends to form lumps upon storage, and is slow to dissolve in solvents. Therefore it is often supplied in solution form, dissolved in organic solvent, water, or organic solvent-water combinations, for example ethanol-water and propylene glycol-water. DOSS can also be mixed with a solid diluent, for example sodium benzoate (SB), to produce a mixture (DOSS-SB) with reduced stickiness and improved water dissolution rate. However, the water solubility and dissolution rates of DOSS-SB mixtures are still low. Sodium benzoate is used as a food preservative and is pharmacologically active. However, its use as an excipient for other active pharmaceutical ingredients can be undesirable, because it is not biologically inert, and because of the risk of formation of benzene from sodium benzoate in the presence of ascorbic acid.
A dialkyl sulfosuccinate composition containing a solid diluent that is free of sodium benzoate, and yet is not waxy or sticky, has good flowability and water solubility, and dissolves rapidly in water, is desirable. Also, the surface and wetting activity of the dialkyl sulfosuccinate, as indicated by critical micelle concentration and contact angle of aqueous solutions of the dialkyl sulfosuccinate with various substrates, should not be adversely affected by the solid diluent.